Oral Iron in Pregnant Women: How Often to Take It and Its Side Effects and Tolerability

Iron Supplementation Frequency and Tolerability in Pregnancy

The goal of this prospective observational study is to examine the frequency of gastrointestinal side effects associated with oral iron supplementation during pregnancy. The main question it aims to answer is:

Does intermittent oral iron supplementation result in fewer gastrointestinal side effects compared with daily supplementation in pregnant women? Pregnant women who are prescribed oral iron as part of their routine medical care will take ferrous sulfate on an alternate-day schedule for one week. If no significant gastrointestinal side effects are reported, they will then take ferrous sulfate daily for an additional week and will be followed for one month. Participants will be contacted by the study investigator to report gastrointestinal side effects, and routine blood tests will be used to assess changes in hemoglobin and iron stores.

This prospective observational study will be conducted in pregnant women who are prescribed oral iron supplementation as part of their routine prenatal care. The study is designed to reflect standard clinical practice and does not introduce any investigational treatment or deviation from accepted management.

Following enrollment, participants will receive oral ferrous sulfate in accordance with common clinical recommendations. The study includes two sequential exposure periods: an initial alternate-day dosing phase followed by a daily dosing phase, provided that no significant gastrointestinal intolerance is reported during the first phase.

At baseline, relevant demographic and pregnancy-related information will be recorded, including maternal age and gestational age at initiation of iron therapy. Baseline laboratory values related to iron status (including hemoglobin and iron stores) will be documented if obtained as part of routine care.

Participants will be instructed to take oral iron according to the prescribed schedule and to continue their usual diet and prenatal care. No dietary restrictions will be imposed as part of the study. Information regarding timing of iron intake, concomitant food consumption (including dairy products), and adherence will be collected through participant self-report.

Participants will be contacted by the study investigator at predefined time points during the supplementation period. Structured interviews will be used to assess gastrointestinal side effects, including constipation, abdominal pain, nausea, vomiting, diarrhea, bloating, and heartburn. Participants will be asked whether symptoms are new, worsened, or unchanged compared with baseline.

At one month after initiation of iron supplementation, participants will undergo follow-up blood tests as part of routine clinical monitoring to assess hemoglobin concentration and iron stores.

Inclusion Criteria:

• Pregnant women aged 18-50
• Indication for oral iron treatment as determined by the treating physician, in accordance with standard clinical practice
• Baseline iron store levels measured prior to initiation of oral iron therapy

Exclusion Criteria:

• Women taking ferrous sulfate 80 mg Tardiferon
• Gastrointestinal diseases such as colitis
• Women who received intravenous iron during pregnancy
• Women who received blood transfusions during pregnancy
• Women with anemia due to causes other than iron deficiency
• History of bariatric surgery
• Allergy to ferrous sulfate